Metal oxide-containing nanoparticles

ABSTRACT

The present invention provides a copper oxide-containing composition that includes copper oxide nanoparticles and one or more heteroatom donor ligands bonded to the surface of the nanoparticles, where x and y are numbers having a ratio that is equal to the ratio of the average number of M atoms to the average number of 0 atoms in the nanoparticles. The nanoparticles are stabilized by the one or more heteroatom donor ligands which act as a protective layer that cap the surface of the nanoparticles. The present invention also provides a solution of the copper oxide nanoparticles that may be applied to a substrate and then subsequently reduced to copper metal. Finally, the invention provides a method of preparing the copper oxide nanoparticles.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to metal oxide-containing nanoparticlesand to methods of making said metal oxide-containing nanoparticles; andin particular to copper oxide-containing nanoparticles that arereducible to copper metal by heating or by contacting with a reducingagent.

2. Background Art

Semiconductor technology increasingly requires the fabrication of fasterand more densely packed integrated circuits. This increasing demandnecessitates better control of conductive interconnects. Of particularinterest is the formation of interconnects in trenches with high aspectratios. It is anticipated that aspect ratios of 1.9 or higher will berequired within the next decade. Currently, the most common methods offorming interconnects are by physical vapor deposition, chemical vapordeposition, or electrochemical deposition. Aluminum and copper are themost common metals used for this purpose. In the typical application,trenches and other structures are overfilled with copper. Wafers treatedin such a manner are then subjected to chemical mechanical polishingwhich is somewhat tedious and causes the surface of the interconnect tobe curved. Moreover, each of these techniques is somewhat susceptible todefects. More importantly, the vacuum coating technologies such asphysical vapor deposition and chemical vapor deposition requiresignificant capital equipment costs and are not able to achieve veryhigh aspect ratios.

Metal nanoparticles have been recognized as potentially useful informing conductive interconnects in such semiconductor devices. Thenanoparticle size range is typically taken to be from about 1 nm toabout 100 nm. Particles of such dimensions exhibit unusual propertieswhich may advantageously be applied when forming interconnects. Althoughsuch nanoparticles exhibit some collective atomic behavior, surface andquantum effects may be important. The lower melting points of nanosizedmetal particles make such particles attractive for interconnecttechnology. Such reduction in melting point can be over 500° C. withmelting points of less than 350° C. attainable for many nanosizedmetals. In the typical application, a dispersed solution containing thenanoparticles is applied to a substrate having trenches by spin coatingor some other dispersal technique. The nanoparticles will preferentiallyaggregate in the trenches. The substrate is then heated to sinter and/ormelt the nanoparticles together thereby forming the interconnect.

U.S. patent application No. 20030008145 discloses a method of maltingmetal nanocrystals that include passivating ligands. The metalnanoparticles of this application have enhanced solubility and/ordispersion because of the passivating ligands associated with thenanocrystals. However, metal containing nanoparticles are somewhatundesirable because of the increased reactivity of such particles and inparticular to the potentially violent oxidation reaction that may occurin the presence of oxygen, water, or certain organic compounds.

Accordingly, there exists a need in the prior art for improved methodsof making metal interconnects and for precursors for making suchinterconnects that are both economical and stable.

SUMMARY OF THE INVENTION

The present invention overcomes the problems of the prior art byproviding a metal oxide-containing composition that includesnanoparticles described on average by Formula I:M_(x)O_(y)   I; andone or more heteroatom donor ligands bonded to the surface of thenanoparticles, where M is a metal; O is oxygen; and x and y are numbershaving a ratio that is equal to the ratio of the average number of Matoms to the average number of O atoms in the nanoparticles. Typically,x and y will be reduced to simpler ratios by methods known to thoseskilled in the art. The nanoparticles are stabilized by the one or moreheteroatom donor ligands which act as a protective layer that cap thesurface of the nanoparticles. This allows for long-term stability andallows the nanoparticles to be readily modified to adjust solubility ina wide range of solvents. Moreover, the nanoparticles may be preparedhaving a variety of metal to oxygen ratios. The metal oxide-containingnanoparticles of the present invention typically have a narrow sizedistribution having mean sizes in the range of 1 nm to 10 nm indiameter.

In another embodiment of the present invention, a metal oxidenanoparticle-containing solution which takes advantage of theadjustability of the solubility of the metal oxide-containingnanoparticles is provided. The metal oxide-containing solution of theinvention comprises the metal oxide composition set forth above and asolvent in which the metal oxide-containing nanoparticles are soluble.

In yet another embodiment of the present invention, a method for makingmetal oxide-containing nanoparticles is provided. The method of theinvention comprises reacting solution of a metal ion solution with aheteroatom donor ligand to form a metal complex. The complex is nextreacted with a reducing agent to form the metal oxide-containingnanoparticles. In a refinement of this embodiment, the metaloxide-containing nanoparticles are advantageously reduced to bulk metalupon heating at modest temperatures under an inert atmosphere. Thetemperature of reduction is believed to vary as a function ofnanoparticle diameter. Thermal reduction of bulk copper oxides to copperhas not been observed at temperatures less than 800° C. Accordingly,such copper oxide-containing nanoparticles have potential application asprecursors to high purity, low resistivity copper films and may serve asa means of filling sub-micron features on silicon wafers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a transmission electron micrograph (“TEM”) ofpyridine-protected Cu₂O nanoparticles of the present invention.

FIG. 2 are the plots of simultaneously performed differential thermalanalysis and thermogravimetric analysis of the Cu₂O nanoparticles of thepresent invention.

FIG. 3 is a plot of the thermogravimetric analysis and its derivativecurve for the Cu₂O nanoparticles of the present invention.

FIG. 4 is the powder X-ray diffraction (“XRD”) of the Cu₂O nanoparticlesof the present invention after heating to 800° C. under inertatmosphere.

FIG. 5 is the XRD of the Cu₂O nanoparticles of the present inventionafter heating to 300° C. under inert atmosphere.

FIG. 6 is the XRD of the Cu₂O nanoparticles of the present inventionafter heating to 400° C. under inert atmosphere.

FIG. 7 are the plots of simultaneously performed differential thermalanalysis and thermogravimetric analysis of unbound 2,2′-bipyridine.

FIG. 8 are the plots of simultaneously performed differential thermalanalysis and thermogravimetric analysis of copper(II) complex of2,2′-bipyridine.

FIG. 9 are the plots of simultaneously performed differential thermalanalysis and thermogravimetric analysis of bulk Cu₂O.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Reference will now be made in detail to presently preferred compositionsor embodiments and methods of the invention, which constitute the bestmodes of practicing the invention presently known to the inventors.

In an embodiment of the present invention, a metal oxide-containingcomposition is provided. The composition of the present inventioncomprises nanoparticles described on average by Formula I:M_(x)O_(y)   I; andone or more heteroatom donor ligands bonded to the surface of thenanoparticles, wherein

-   -   M is a metal;    -   O is oxygen; and

x and y are numbers having a ratio that is equal to the ratio of theaverage number of M atoms to the average number of O atoms in thenanoparticles. Preferably, M is a metal selected from beryllium,magnesium, aluminum, scandium, titanium, vanadium, chromium, manganese,iron, cobalt, nickel, copper, zinc, gallium, germanium, yttrium,zirconium, niobium, molybdenum, technetium, ruthenium, rhodium,palladium, silver, cadmium, indium, tin, antimony, lanthanum, cerium,praseodymium, neodymium, promethium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium,hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold,thallium, lead, bismuth, polonium, thorium, protactinium, uranium,neptunium, and plutonium. More preferably M is a metal selected fromGroup 9 through Group 11 elements; and most preferably, M is copper withthe metal oxide nanoparticles having formula II:Cu_(x)O_(y)   II

The average number of metal atoms and oxygen atoms in the nanoparticlesis calculated from the range of possible mean diameters of thenanoparticles which is from about 1 nm to about 1000 nm. Morepreferably, the range of possible mean diameters is from about 1 nm toabout 100 nm; and most preferably the mean diameters of thenanoparticles is less than about 20 nm. Preferably, the number of metalatoms M is from about 10 to about 5×10¹⁰. More preferably, the number ofmetal atoms M is from about 10 to about 5×10⁹; and most preferably thenumber of metal atoms M is less than about 4.0×10⁵ atoms. The number ofO atoms is preferably equal to at least about 0.01 times the number of Matoms. More preferably, the number of O atoms is equal to at least about0.1 times the number of M atoms; and most preferably, the number of Oatoms is equal to at least about 0.3 times the number of M atoms.Similarly, y is preferably equal to at least 0.01×. More preferably y isequal to at least 0.1×; and most preferably, y is equal to at least0.3×. Typically, x and y will be reduced to simpler ratios by methodsknow to those skilled in the art. The maximum value for y is about thatamount necessary to satisfy the valence of the highest oxidation stateof the metal. However, slightly more oxygen may be present because ofoxygen-based defects in the nanoparticles. Preferably, y is equal to orless than 5×. More preferably y is equal to or less than about 3×. Forexample, for a nanoparticle of 200 M atoms and 100 O atoms the formulawill be expressed as M₂O. The nanoparticles of the present invention maybe crystalline (nanocrystals) or may be amorphous. The typicalnanoparticles are spherical particles, but other shapes may be suitable.Metal oxide containing nanoparticles of the following morphologies areof potential interest: spherical, ellipsoidal, rod-shaped, polyhedral,as well as others.

The metal atoms of the nanoparticles may be of uniform oxidation stateor may be present as mixtures of oxidation states. Different oxidationstates of the metal are one or more of the values selected from 0, +1,+2, +3, +4, +5, +6, +7, and +8. In the case of copper, the most likelycopper oxidation states are 0, +1, and +2, but others are possible. Thetypical copper oxide nanoparticle preparation (as given in synthesisdescription below) results in particles that are uniformly composed ofcuprite, Cu₂O.

The nanoparticles are protected from oxidation and/or agglomeration byvirtue of a protective (or passivating) layer by the one or moreheteroatom donor ligands that are chemically bonded to the surfaces ofthe nanoparticles. The nature of the protective ligand allows for thenanoparticles to be dissolved or finely dispersed in a variety of liquidsolvents. The protective ligands can easily be tailored by adding orchanging functional groups such that a high degree of solubility isachieved in the solvent of choice. For example, by using 2,2′-bipyridineas the protective ligand copper oxide particles can be prepared that aresoluble in methanol, ethanol, 1-propanol, isopropanol, 1-butanol,acetone, dichloromethane, ethylene glycol, as well as other polarsolvents. By using 2,2′-bipyridine to which long alkyl chains haveattached to the aromatic ring, solubility in non-polar solvents has beenachieved. Another example is where the protective ligand is derived fromdecanoic acid whereby the copper oxide nanoparticles are soluble innon-polar solvents such as hexane. By such a strategy it is envisionedthat particles could be made to exhibit solubility in solvents rangingfrom polar, hydrogen-bonding solvents to non-polar hydrocarbon speciesand their perfluorinated derivatives, including hexanes andperfluoromethylcyclohexane.

Protecting ligands include all compounds containing an oxygen ornitrogen atom that is capable of acting as an electron-pair donor toform a bond to the nanoparticle surface. Nitrogen donor examplesinclude, but are not limited to, alkyl, amines, pyridine,2,2′-bipyridine, pyrrole, pyrazole, imidazole, triazole, tetrazole,nitriles, and any substituted variations and salts thereof. Oxygen donorexamples include, but are not limited to, carboxylic acids, carbonates,nitrates, nitroalkanes, nitroarenes, hydroxamic acids, ketones,aldehydes, esters, and any substituted variations and salts thereof.Furthermore, it is anticipated that some of the most useful protectingligands will have some degree of charge stabilization. The nature ofligands having such capability can be described as follows: a)nanoparticle surface is capped by a ligand as described above whichbears a charge; the charge may be localized on one or more of thedonor-atoms, or localized on one or more of the non-donor atoms, or itmay be delocalized through a number of donor and/or non-donor atoms, b)associated with the charge bearing ligands are some number of oppositelycharged species which may provide additional stabilization arising fromsome combination of steric bulk and the formation of a charge barrier.In addition to the one or more heteroatom donor ligands, the metaloxide-containing composition of the present invention may furtherinclude one or more loosely bound heteroatom ligands. As used herein,loosely bound means that the heteroatom ligands are associated with thenanoparticles, but are not bonded to the nanoparticles as the one ormore heteroatom donor ligands. Such an association may be byelectrostatic interaction. Examples of such ligands include, forexample, a hetereoatom donor ligand (in this instance the heteroatomdonor ligand is not as strongly bonded to the surface of thenanoparticles as described above), nitrate, halide, phosphate,perchlorate, formate, acetate, borate, hydroxide, silicate, carbonate,sulfite, sulfate, nitrite, phosphite, water, or mixtures thereof.

The thermal behavior of the metal oxide nanoparticles is of centralinterest to the present invention, particularly the observed reductionof the metal oxide-containing nanoparticles to bulk metal upon mildheating. The individual thermal events for a typical sample of metaloxide nanoparticles are as follows: loss of unbound and/or loosely boundligand, loss of bound ligand, and reduction of metal oxide nanocrystalsto bulk metal. The loss of unbound and loosely bound ligand is expectedto occur at temperatures at or near the boiling point or sublimationtemperature of the ligand molecule. This would generally occur over anarrow temperature range, somewhere between 50° C. and 250° C.,depending on the ligand and metal. The loss of bound ligand willgenerally occur at a temperature significantly higher than that of theunbound ligand; a certain amount of additional energy is required tobreak bonds to the surface of the nanoparticle. Loss of bound ligandwould generally occur at between 100° C. and 300° C. and may beaccompanied by ligand decomposition. Reduction of copperoxide-containing nanoparticles to copper generally occurs between 300°C. and 500° C., with lower reduction temperatures being preferred. Thetypical preparation (as given below) results in Cu₂O nanoparticleshaving diameters estimated near 4 nm that reduce to bulk copper ataround 380° C. Bulk phase Cu₂O is not reduced upon heating, even withtemperatures as high as 800° C. The observed low-temperature thermalreduction represents a potentially novel, nano-phase phenomenon that isnot known for the bulk-phase of this material. This property, being aresult of the size regime of the material, is strongly believed tobehave as a function of particle size; the reduction temperature shouldvary with nanoparticle diameter as a consequence.

In another embodiment of the present invention, a metal oxide-containingsolution which takes advantage of the adjustability of the solubility ofthe metal oxide-containing nanoparticles is provided. The metaloxide-containing solution of the invention comprises the metal oxidecomposition set forth above and a solvent in which the metaloxide-containing nanoparticles are soluble. As set forth above, thesolubility of the metal oxide-containing nanoparticles is adjustable byappropriate selection of the one or more heteroatom donor ligands. Thismetal oxide-containing solution is particularly useful in applying thenanoparticles to a substrate. Specifically, a substrate is contactedwith a nanoparticle-containing solution and then the solvent isevaporated or allowed to evaporate leaving behind the nanoparticles. Themetal oxide nanoparticles are then optionally converted to zero-valentmetal by heating. In the case of copper oxide-containing nanoparticleswith a mean diameter of about 4 nm, this conversion occurs at atemperature of at least 100° C. Alternatively, the conversion tozero-valent metal is accomplished by contacting the metaloxide-containing nanoparticles with a reducing agent. Suitable reducingagent, include but are not limited to, molecular hydrogen, alcohols,amines, or mixtures thereof.

In yet another embodiment of the present invention, a method for makingmetal oxide-containing nanoparticles is provided. The method of theinvention comprises reacting a metal ion in solution (i.e., from a salt)with a heteroatom donor ligand to form a metal complex. Preferably themole ratio of metal ion to ligand is from about 0.05 to about 20. Morepreferably, the mole ratio of metal ion to ligand is from about 2 to 6.The metal complex is next reacted with a reducing agent to form themetal oxide-containing nanoparticles. For example, to make copperoxide-containing nanoparticles, CuX₂ is reacted with a heteroatom donorligand to form a copper complex. Preferably the mole ratio of CuX₂ toligand is from about 0.05 to about 20. More preferably, the mole ratioof CuX₂ to ligand is from about 0.5 to 10; most preferably the moleratio of CuX₂ to ligand is from about 2 to 6. The copper complex is nextreacted with a reducing agent to form the copper oxide-containingnanoparticles. Suitable reducing agents include, but are not limited to,sodium borohydride, lithium aluminum hydride, molecular hydrogen, sodiummetal, zinc metal, magnesium metal, aluminum metal, hydrazine, and thelike. X is a metal ion counterion. Suitable examples for X include, butare not limited to, halide, nitrate, phosphate, perchlorate, formate,acetate, borate, hydroxide, silicate, carbonate, sulfite, sulfate,nitrite, phosphite, hydrates thereof; and mixtures thereof. Theproperties of the metal oxide-containing nanoparticles, preferred andsuitable metals M, and suitable heteroatom donor ligands are the same asthose set forth above for the metal oxide-containing composition setforth above.

The method of the present invention also optionally includes the step ofreacting the metal oxide-containing nanoparticles at a sufficiently hightemperature to form metal. In the case of copper oxide-containingnanoparticles, the copper oxide-containing nanoparticles are heated to atemperature of at least 100° C. Alternatively, the conversion to metalis accomplished by contacting the metal oxide nanoparticles with asecond reducing agent. Suitable second reducing agents, include but arenot limited to, molecular hydrogen, alcohols, amines, or mixturesthereof.

The following examples illustrate the various embodiments of the presentinvention. Those skilled in the art will recognize many variations thatare within the spirit of the present invention and scope of the claims.

Synthesis of Copper Oxide Nanoparticles

Described herein is a typical synthesis of copper oxide nanoparticles asdescribed by Scheme I. The particles obtained consist of Cu₂O, estimatedto be about 4.mn in size, having a 2,2′-bipyridine (“bipy”) protectiveligand coat. The synthesis is readily scalable, typically giving highyields (>80%, >2 g) of a free-flowing reddish-brown powder. The productis soluble in polar organic solvents such as methanol, ethanol, acetone,and dichloromethane, as well as others. The solid form of the sample canbe readily achieved from solutions by removal of solvent under reducedpressure. As a solid, the sample is stable indefinitely if stored atroom temperature under argon. The solution is stable for at least onemonth in an oxygen and moisture free environment. Upon long-termexposure to air, the solid sample retains its properties for at leastone week. The sample in solution typically begins to show signs ofdecomposition after few hours of exposure to air.

1. Synthetic Example

Aqueous copper(II) nitrate (0.167 M, 150 mL) was treated with2,2′-bipyridine (3.905 g, 0.025 mol) under rapid stirring. Aqueoussodium borohydride (5.0 mM, 80 mL) was added dropwise to the rapidlystirring solution, which had been cooled to 0° C. Upon reduction thereaction mixture became dark reddish-brown in color. As a brownprecipitate began to form, the vigorous effervescence of the reactionmixture led to foaming. Stirring was continued, making occasionaladjustments so as to accommodate foaming. Upon cessation of foaming andeffervescence a dark brown solid was isolated by vacuum filtration. Thesoluble material was then extracted by treating the solid with severalportions of absolute ethanol until the filtrate was colorless. Thefiltrate was taken to dryness and washed with 20 mL of tetrahydrofuran(“THP”) to remove excess ligand. Using standard Schlenk techniques underinert atmosphere, soluble nanoparticles were extracted from the residueusing three 40 mL portions of CH₂Cl₂. The solution was taken to drynessunder vacuum to afford a rust-colored powder that could be readilyredissolved in polar organic solvents.

2. Characterization of Copper Oxide-Containing Nanoparticles

A number of methods of characterization have been used to study thecopper oxide-containing nanoparticles. Proton Nuclear Magnetic Resonance(1H NMR) of the sample revealed signals that are consistent with theprotons of the protecting ligand (in the above case 2,2′-bipyridine).Infrared absorption spectroscopy (IR) for the sample is also consistentwith the presence of the protecting ligand (in the above case2,2′-bipyridine), but also shows peaks that suggest the presence ofnitrate, which may be present also as a bound ligand. Powder X-raydiffraction (XRD) data for the sample is inconclusive and may indicatethat the particles are amorphous or are very small nanoparticles.

Transmission electron microscopy images have been collected for a copperoxide-containing nanoparticle sample where the ligand is 2,2′-bipyridineand for the analogous pyridine-capped nanoparticle sample. Themicrographs from the 2,2′-bipyridine protected sample were consistentwith particles of a size on the order of 4 nm. The micrographs of thepyridine-capped copper oxide-containing particles convincingly displayrelatively monodisperse particles of a mean size near 5.5 nm (FIG. 1).The transmission electron micrograph for these nanoparticles prepareddisplays both spherical and near-spherical particles having a meandiameter of 5.46 nm. The standard deviation in particle diameter is 1.18nm (˜20% the mean diameter), indicative of a reasonably narrowdistribution of size. A number of the particles exhibit distinct latticefringes, as would be expected for nanocrystals. For other particles thelattice fringes are indistinct or absent. Particles lacking latticefringes may either be amorphous, lacking a well-defined lattice, or maybe crystalline, but positioned in such a way that the lattice is notreadily observed. The transmission electron micrograph for cupritenanoparticles prepared with 2,2′-bipyridine as the capping ligand alsodisplays spherical and near-spherical particles. The mean diameter ofthe particles is 3.82 nm, with a standard deviation of 0.81 nm. Again,the particles exhibit a reasonably narrow size distribution, with thestandard deviation being ˜20% of the mean diameter. Lattice fringes areobserved for a number of the particles.

Differential thermal analysis (DTA) and thermogravimetric analysis (TGA)were performed simultaneously on a solid sample of 2,2′-bipyridineprotected copper oxide-containing nanoparticles (FIGS. 2 and 3). Fourregions of interest were found in the DTA of the sample: an endotherm at201° C., an exotherm at 262° C., an endotherm at 301° C., and anexotherm at 377° C. The TGA exhibited two major regions of weight loss:a loss of 39% of the sample weight centered at 249° C., and a loss of 8%centered at 374° C. The DTA/TGA residue after heating to 800° C. in aninert atmosphere was determined to be bulk copper by XRD (FIG. 4).Heating the sample to 300° C. under DTA/TGA conditions yielded materialthat was identified by XRD as being predominantly Cu₂O, where thecrystalline domain was small (<10 nm) as determined by line broadening(FIG. 5). Upon heating to 400° C., the residue was observed to becomebulk phase copper as determined by XRD (FIG. 6).

To understand better the implications of the DTA/TGA data, DTA/TGA wasperformed on a series of reference materials. The endothern at 201° C.correspond well to that observed for the volatilization point of unbound2,2′-bipyridine (FIG. 7). The fact that this endotherm is notaccompanied by a weight loss for the nanoparticle sample indicates thatthe amount of unbound (or loosely bound) 2,2′-bipyridine in the sampleis small. The exotherm at 262° C. and the weight loss centered at 249°C. appear to concur with the loss of bound 2,2′-bipyridine as determinedby comparison to the DTA/TGA of the copper(II) complex of2,2′-bipyridine (FIG. 8). The exotherm at 377° C. and the concurrentweight loss at 374° C. are clearly due to the loss of oxygen from Cu₂Oto give copper as stated above. DTA/TGA was performed on a sample ofbulk Cu₂O (FIG. 9); no thermal features were observed. The residue wasfound to be bulk Cu₂O after heating to 800° C. under inert atmosphere.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

1. A metal oxide-containing composition, the composition comprising:metal oxide nanoparticles described on average by Formula I:M_(x)O_(y)   I; and one or more heteroatom donor ligands bonded to thesurface of the nanoparticles, wherein M is a metal; O is oxygen; and xand y are numbers having a ratio that is equal to the ratio of theaverage number of M atoms to the average number of O atoms in thenanoparticles, wherein the number of M atom is from about 10 to about5×10¹⁰ atoms and the number of O atoms is at least about 0.01 times thenumber of M atoms.
 2. The metal oxide-containing composition of claim 1wherein M is a metal selected from beryllium, magnesium, aluminum,scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel,copper, zinc, gallium, germanium, yttrium, zirconium, niobium,molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium,indium, tin, antimony, lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolimium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, hafnium, tantalum,tungsten, rhenium, osmium, iridium, platinum, gold, thallium, lead,bismuth, polonium, thorium, protactinium, uranium, neptunium, andplutonium.
 3. The metal oxide-containing composition of claim 1 whereinM is a metal selected from Group 9 through Group 11 elements.
 4. Themetal oxide- containing composition of claim 1 wherein the one or moreheteroatom donor ligands include compounds containing an oxygen ornitrogen atom that are capable of acting as an electron-pair donor toform a bond to the surface of the nanoparticles.
 5. The metaloxide-containing composition of claim 1 wherein the one or moreheteroatom donor ligands are selected from the group consisting of alkylamines, pyridine, 2,2′-bipyridine, pyrrole, pyrazole, imidazole,triazole, tetrazole, nitriles, carboxylic acids, carbonates, nitrates,nitroalkanes, nitroarenes, hydroxamic acids, ketones, aldehydes, andesters.
 6. The metal oxide-containing composition of claim 1 wherein thenanoparticles have a mean diameter from about 1 nm to 1000 nm.
 7. Themetal oxide-containing composition of claim 1 wherein the nanoparticleshave a mean diameter from about 1 nm to 100 nm.
 8. The metaloxide-containing composition of claim 1 wherein the nanoparticles have amean diameter less than about 20 nm.
 9. The metal oxide-containingcomposition of claim 1 wherein the nanoparticles have a spherical,ellipsoidal, rod-shaped, or polyhedral morphology.
 10. The metaloxide-containing composition of claim 1 wherein the metal oxidenanoparticles include amorphous or crystalline domains.
 11. The metaloxide-containing composition of claim 1 wherein the nanoparticlesinclude a mixture of metal atoms in different oxidation states.
 12. Themetal oxide-containing composition of claim 10 wherein the differentoxidation states are one or more of the values selected from 0, +1, +2,+3, +4, +5, +6, +7, and +8.
 13. The metal oxide-containing compositionof claim 1 further comprising one or more loosely bound heteroatomligands.
 14. The metal oxide-containing composition of claim 13 whereinthe one or more loosely bound heteroatom ligands are nitrate, halide,phosphate, perchlorate, formate, acetate, borate, hydroxide, silicate,carbonate, sulfite, sulfate, nitrite, phosphite, water, alkyl amines,pyridine, 2,2′-bipyridine, pyrrole, pyrazole, imidazole, triazole,tetrazole, nitriles, carboxylic acids, carbonates, nitrates,nitroalkanes, nitroarenes, hydroxamic acids, ketones, aldehydes, estersor mixtures thereof.
 15. A metal oxide-containing solution, the solutioncomprising: a solvent; metal oxide nanoparticles described on average byFormula I:M_(x)O_(y)   I; and one or more heteroatom donor ligands bonded to thesurface of the nanoparticles, wherein M is a metal; O is oxygen; and xand y are numbers having a ratio that is equal to the ratio of theaverage number of M atoms to the average number of O atoms in thenanoparticles, wherein the number of M atom is from about 10 to about5×10¹⁰ atoms and the number of O atoms is at least about 0.01 times thenumber of M atoms.
 16. The metal oxide-containing solution of claim 15wherein the heteroatom donor ligand is derived from decanoic acid andthe solvent is hexane.
 17. The metal oxide-containing solution of claim15 wherein the heteroatom donor ligand is 2,2′-bipyridine and thesolvent is a polar solvent.
 18. The metal oxide-containing solution ofclaim 15 wherein the solvent comprises at least one compound selectedfrom the group consisting of methanol, ethanol, 1-propanol, isopropanol,1-butanol, acetone, dichloromethane, and ethylene glycol.
 19. The metaloxide-containing solution of claim 15 wherein the heteroatom donorligand is 2,2′-bipyridine to which long chain alkyls have been attachedand the solvent is a nonpolar solvent.
 20. A method of applying metaloxide-containing nanoparticles to a substrate, the method comprising: 1)contacting the substrate with the solution of claim 15; and 2)evaporating the solvent or allowing the solvent to evaporate.
 21. Themethod of claim 20 further comprising: 3) heating the metaloxide-containing nanoparticles at a sufficiently high temperature toform zero-valent metal.
 22. The method of claim 21 wherein the metaloxide nanoparticles are heated to a temperature of at least 200° C. 23.The method of claim 20 further comprising contacting the metal oxidenanoparticles with a reducing agent.
 24. The method of claim 23 whereinthe reducing agent is selected from the group consisting of molecularhydrogen, alcohols, amines, or mixtures thereof.
 25. A copperoxide-containing composition, the composition comprising: copper oxidenanoparticles described on average by Formula I:Cu_(x)O_(y)   II; and one or more heteroatom donor ligands bonded to thesurface of the nanoparticles, wherein Cu is copper; O is oxygen; and xand y are numbers having a ratio that is equal to the ratio of theaverage number of Cu atoms to the average number of O atoms in thenanoparticles, wherein the number of Cu atoms is from about 10 to about5×10¹⁰ atoms and the number of O atoms is at least about 0.01 times thenumber of Cu atoms.
 26. The copper oxide-containing composition of claim25 wherein the one or more heteroatom donor ligands include compoundscontaining an oxygen or nitrogen atom that is capable of acting as anelectron-pair donor to form a bond to the surface of the nanoparticles.27. The copper oxide-containing composition of claim 25 wherein the oneor more heteroatom donor ligands are selected from the group consistingof alkyl amines, pyridine, 2,2′-bipyridine, pyrrole, pyrazole,imidazole, triazole, tetrazole, nitrites, carboxylic acids, carbonates,nitrates, nitroalkanes, nitroarenes, hydroxamic acids, ketones,aldehydes, and esters.
 28. The copper oxide-containing composition ofclaim 25 wherein the nanoparticles have an mean diameter from about 1 nmto 1000 nm.
 29. The copper oxide-containing composition of claim 25wherein the nanoparticles have an mean diameter from about 1 nm to 100nm.
 30. The copper oxide-containing composition of claim 25 wherein thenanoparticles have an mean diameter less than about 20 nm.
 31. Thecopper oxide-containing composition of claim 25 wherein thenanoparticles have a spherical, ellipsoidal, rod-shaped, or polyhedralmorphology.
 32. The copper oxide-containing composition of claim 25wherein the copper oxide nanoparticles are amorphous or crystalline. 33.The copper oxide-containing composition of claim 25 wherein thenanoparticles include a mixture of copper atoms in different oxidationstates.
 34. The copper oxide-containing composition of claim 32 whereinthe different oxidation states are 0, +1, and +2.
 35. The copperoxide-containing composition of claim 25 further comprising one or moreloosely bound heteroatom ligands.
 36. The copper oxide-containingcomposition of claim 35 wherein the one or more additional heteroatomcontaining molecules are nitrate, halide, phosphate, perchlorate,formate, acetate, borate, hydroxide, silicate, carbonate, sulfite,sulfate, nitrite, phosphite, water, alkyl amines, pyridine,2,2′-bipyridine, pyrrole, pyrazole, imidazole, triazole, tetrazole,nitriles, carboxylic acids, carbonates, nitrates, nitroalkanes,nitroarenes, hydroxamic acids, ketones, aldehydes, esters, or mixturesthereof.
 37. A copper oxide-containing solution, the solutioncomprising: copper oxide nanoparticles described on average by FormulaI:Cu_(x)O_(y)   II; one or more heteroatom donor ligands bonded to thenanoparticles; and a solvent, wherein Cu is copper; O is oxygen; and xand y are numbers having a ratio that is equal to the ratio of theaverage number of Cu atoms to the average number of O atoms in thenanoparticles, wherein the number of Cu atoms is from about 10 to about5×10¹⁰ atoms and the number of O atoms is at least about 0.01 times thenumber of Cu atoms.
 38. The copper oxide-containing solution of claim 37wherein the heteroatom donor ligand is derived from decanoic acid andthe solvent is hexane.
 39. The copper oxide-containing solution of claim37 wherein the heteroatom donor ligand is 2,2′-bipyridine and thesolvent is a polar solvent.
 40. The copper oxide-containing solution ofclaim 37 wherein the solvent comprises a component selected from thegroup consisting of methanol, ethanol, 1-propanol, isopropanol,1-butanol, acetone, dichloromethane, and ethylene glycol.
 41. The copperoxide-containing solution of claim 37 wherein the heteroatom donorligand is 2,2′-bipyridine to which long chain alkyls have been attachedand the solvent is a nonpolar solvent.
 42. A method for making metaloxide-containing nanoparticles, the method comprising: reacting a metalion in solution with a heteroatom donor ligand to form a metal complex;and reducing the metal complex with a reducing agent to form the metaloxide-containing nanoparticles.
 43. The method of claim 42 wherein themetal ion solution is formed by dissolving a metal salt in a solution.44. The method of claim 42 wherein the mole ratio of metal ion to ligandis from about 0.05 to about
 20. 45. A method for making copperoxide-containing nanoparticles, the method comprising: 1) reacting CuX₂with a heteroatom donor ligand to form a copper complex; and 2) reactingthe copper complex with a first reducing agent to form the copperoxide-containing nanoparticles, wherein X is a metal ion counterion. 46.The method of claim 45 wherein X is selected from the group consistingof halide, nitrate, phosphate, perchlorate, formate, acetate, borate,hydroxide, silicate, carbonate, sulfite, sulfate, nitrite, phosphite,hydrates thereof; and mixtures thereof.
 47. The method of claim 45wherein the one or more heteroatom donor ligands include compoundscontaining an oxygen or nitrogen atom that is capable of acting as anelectron-pair donor to form a bond to the surface of the nanoparticles.48. The method of claim 45 wherein the one or more heteroatom donorligands are selected from the group consisting of alkyl amines,pyridine, 2,2′-bipyridine, pyrrole, pyrazole, imidazole, triazole,tetrazole, nitriles, carboxylic acids, carbonates, nitrates,nitroalkanes, nitroarenes, hydroxamic acids, ketones, aldehydes, andesters.
 49. The method of claim 45 wherein the copper oxide-containingnanoparticles include a mixture of copper atoms in different oxidationstates.
 50. The method of claim 49 wherein the different oxidationstates are 0, +1, and +2.
 51. The method of claim 45 wherein the firstreducing agent is sodium borohydride, lithium aluminum hydride,molecular hydrogen, sodium metal, zinc metal, magnesium metal, aluminummetal, or hydrazine.
 52. The method of claim 45 wherein the copper oxidenanoparticles comprise Cu₂O.
 53. The method of claim 45 wherein thecopper oxide nanoparticles have a diameter from about 1 nm to about 100nm.
 54. The method of claim 45 wherein the copper oxide nanoparticleshave a diameter less than about 20 nm.
 55. The method of claim 45wherein the copper oxide nanoparticles are amorphous or crystalline. 56.The method of claim 45 further comprising: 3) heating the copperoxide-containing nanoparticles to a sufficiently high temperature toform copper metal.
 57. The method of claim 45 wherein the copper oxidenanoparticles are heated to a temperature of at least 200° C.
 58. Themethod of claim 45 further comprising contacting the copper oxidenanoparticles with a second reducing agent.
 59. The method of claim 58wherein the second reducing agent is selected from the group consistingof molecular hydrogen, alcohols, amines, or mixtures thereof.